Polyurethanes prepared from polyester organic diisocyanates and bis-(beta-hydroxyethoxy-phenyl)methane

ABSTRACT

ELASTOMERIC POLYURETHANE POLYMERS ARE PREPARED BY REACTING A POLYISOCYANATE WITH AN ORGANIC COMPOUND HAVING ACTIVE HYDROGEN ATOMS WHICH ARE REACTIVE WITH -NCO GROUPS AND BIS-(B-HYDROXYETHOXYPHENYL)METHANE AS A CHAIN-EXTENDER. THE ELASTOMERS HAVE GOOD PHYSICAL PROPERTIES AND IMPROVED RESISTANCE TO HYDROLYSIS.

United States Patent US. Cl. 260-47 CB 5 Claims ABSTRACT OF THEDISCLOSURE Elastomeric polyurethane polymers are prepared by reacting apolyisocyanate with an organic compound having active hydrogen atomswhich are reactive with NCO groups andbis-(B-hydroxyethoxyphenyl)methane as a chain-extender. The elastomershave good physical properties and improved resistance to hydrolysis.

FIELD OF INVENTION This invention relates to polyurethane polymers andto a method of preparing the same. More particularly, the inventionrelates to elastomeric polyurethane polymers of improved physical andmechanical properties and having improved resistance to hydrolysis andto a method of preparing the same.

DISCUSSION OF PRIOR ART The production of cross-linked synthetic resinsbased on polyhydroxyl compounds, polyisocyanates and chain lengtheningagents or cross-linking agents having reactive hydrogen atoms such asglycols, diamines, aminoalcohols and the like has been heretofore known.The proportions may be so chosen that free -NCO groups remain and themolten reaction mixture may be poured into molds, cross-linkages beingformed by way of allophanate groups, biuret groups, by polymerization orthe like after it has been poured. Elastomeric shaped articles areobtained. Alternatively, the NCO groups which remain may be stabilizedor the process may be carried out with equivalent quantities or with anexcess of reactive hydrogen atoms. By this method there are obtainedpolyurethane compositions which can be stored and which can becross-linked with cross-linking agents in a man ner similar to cruderubber by the usual methods of the rubber industry, for example, onrollers. However, the elastomers obtained in many cases have onlyrelatively low tensile strengths at elongations of from about 300% toabout 500%. Fillers have heretofore been used to increase the modulussomewhat, but do not improve the ultimate tensile strength. Moreover, inmany cases the elastomers do not retain an acceptable portion of theirtensile strength when subjected to conditions of hydrolysis aging.

OBJECTS It is, therefore, an object of this invention to providepolyurethane polymers and a method of preparing the same which aredevoid of the aforesaid problems and disadvantages. Another object ofthis invention is to provide improved polyurethane polymers. Anadditional object of this invention is to provide a method of preparingimproved polyurethane polymers. A further object of this invention is toprovide polyurethane polymers having a desirable combination ofproperties and to a process of preparing the same. A still furtherobject of this invention is to provide a method for the preparation ofpolyurethane polymers having a wide range ofdesirable mechanical andphysical properties. Yet another object of this invention is to provideelas- 3,711,440 Patented Jan. 16, 1973 tomeric, nonporous polyurethanepolymers having improved retention of tensile strength upon being subect to conditions of hydrolysis aging.

SUMMARY OF THE INVENTION The foregoing objects and other which willbecome apparent from the following description are accomplished inaccordance with this invention, generally speaking, by providingpolyurethane polymers prepared by reacting a substantially linearcompound having active hydrogen atoms as determined by the Zerewitinotftest, which active hydrogens are reactive with isocyanato groups, and anexcess of an organic polyisocyanate with a chain extending agentcomprising bis(fl-hydroxyethoxyphenyl)methane in an amount at leastsuflicient to react with all the -NCO groups of the reaction productobtained from the organic compound having active hydrogen atoms and theorganic isocyanate. Thus, the invention contemplates the preparation ofelastomeric polyurethane polymers wherein the chain extender set forthabove is used in place of the customarily used chain extending agents.

DETAILED DISCLOSURE OF THE INVENTION This invention is applicable to theproduction of any suitable polyurethane polymer from any suitablesubstantially linear organic compound containing active hydrogen atoms,such as, for example, dihydroxyl polyesters, polyalkylene ether glycols,polythioethers, dihydric polyacetals, polyester amides and the like butit is preferred to use a polyhydric polyalkylene ether, a polyhydricpolythioether and most preferably a hydroxyl polyester obtained by aprocess which comprises condensing a polycarboxylic acid and apolyhydric alcohol.

Any suitable hydroxyl polyester may be used in the process of thisinvention such as, for example, the condensation product of apolycarboxylic acid and a polyhydric alcohol. Any suitablepolycarboxylic acid may be used in the preparation of the hydroxylpolyester such as, for example, adipic acid, succinic acid, sebacicacid, suberic acid, oxalic acid, malonic acid, methyl adipic acid,glutan'c acid, pimelic acid, azelaic acid, phthalic acid, terephthalicacid, isophthalic acid, thiodipropionic acid, maleic acid, fumaric acid,citraconic acid, itaconic acid, and the like. Any suitable polyhydricalcohol may be used in the reaction with the polycarboxylic acid to forma polyester such as, for example, ethylene glycol, propylene glycol,butylene glycol, neopentyl glycol, amylene glycol, hexanediol,bis-(hydroxymethylcyclohexane) and the like. Of course, the hydroxylpolyester may contain urethane groups, urea groups, amide groups,chalkogen groups and the like. Thus, the hydroxyl terminated polyesterincludes, in addition to hydroxyl terminated polyesters, also hydroxylterminated polyester amides, polyester urethanes, polyetheresters andthe like. Any suitable polyester amide may be used such as, for example,the reaction product of a diamine or an amino alcohol with any of thecompositions set forth for preparing polyesters. Any suitable amine maybe used such as, for example, ethylene diamine, propylene diamine,tolylene diamine and the like. Any suitable amino alcohol such as, forexample, fi-hydroxy ethylamine and the like may be used. Any suitablepolyester urethane may be used such as, for example, the reaction of anyof the above-mentioned polyesters or polyester amides with a deficiencyof an organic polyisocyanate to produce a compound having terminalhydroxyl groups. Any of the polyisocyanates set forth hereinafter may beused to prepare such compounds.

Any suitable polyetherester may be used as the organic compoundcontaining terminal hydroxyl groups such as, for example, the reactionproduct of an ether glycol and a polycarboxylic acid such as thosementioned above, with relation to the preparation of polyesters. Anysuitable ether glycol may be used such as, for example, diethyleneglycol, triethylene glycol, 1,4-phenylene-bis-(hydroxy ethyl ether),2,2'-diphenyl propane, 4,4'-bis-(hydroxy ethyl ether) and the like.

Any suitable polyhydric polyalkylene ether may be used such as, forexample, the condensation product of an alkylene oxide with a smallamount of a compound containing active hydrogen containing groups suchas, for example, water, ethylene glycol, propylene glycol, butyleneglycol, amylene' glycol, trimethylol propane, glycerine,pentaerythritol, hexanetriol, arabitol, sorbitol, maltose, sucrose,ammonia, diethenolamine, triethenolamine, 2,4- tolylene diamine and thelike. Any suitable alkylene oxide condensate may also be used such as,for example, the condensates of ethylene oxide, propylene oxide,butylene oxide, amylene oxide, styrene oxide and the like and mixturesthereof. The polyalkylene ethers prepared from tetrahydrofuran may beused. The polyhydric polyalkylene ethers may be prepared by any knownprocess such as, for example, the process described by Wurtz in 1859 andin the Encyclopedia of Chemical Technology, volume 7, pages 257-262,published by Interscience Publishers in 1951 or in US. Pat. 1,922,459.

Any suitable polyhydric polythioether may be used such as, for example,the reaction product of one of the aforementioned alkylene oxides usedin the preparation of the polyhydric polyalkylene ether with apolyhydric thioether such as, for example, thiodiglycol,3,3'-dihydroxypropyl sulfide, 4,4'-dihydroxybutyl sulfide,1,4-(13-hydroxy ethyl) phenylene dithioether and the like.

Any suitable polyacetal may be used such as, for example, the reactionproduct of an aldehyde with a polyhydric alcohol. Any suitable aldehydemay be used such as, for example, formaldehyde, paraldehyde,butyraldehyde and the like. Any of the polyhydric alcohols mentionedabove with relation to the preparation of hydroxyl polyesters may beused.

Mixtures of any of the compounds of the classes set forth hereinabovemay be used also.

The organic compound containing active hydrogen atoms should preferablybe substantially linear or only slightly branched and have a molecularweight of at least about 600 and for best results, a molecular weight offrom about 1000 to about 3000, a hydroxyl number of from about 75 toabout 35 and an acid number less than about 2.

Any suitable organic diisocyaante may be used in reaction with theorganic compound containing active hydrogen atoms to producepolyurethane polymers such as, for example, aliphatic, cycloaliphatic,aromatic and heterocyclic isocyanates, such as alkylene, cycloalkyleneand arylene diisocyanates which may be substituted with substituentsunreactive with active hydrogen and isocyanato groups such as, forexample, ethylene diisocyanate, ethylidene diisocyanate,. propylenediisocyanate, butylene diisocyanate, hexamethylene diisocyanate,cyclopentylene-l, l t-diisocyanate, cyclohexylene-1,4-diisocyanate,cyclohexylene-l,2-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate and their isomeric mixtures, dimeric tolylene diisocyanate,4,4'-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, p-phenylene diisocyanate,m-phenylene diisocyanate, xylylene diisocyanate, 1, 4-naphthylenediisocyanate, 1,5-naphthylene diisocyanate, diphenyl-4,4'-diisocyanate,azobenzene-4,4'-diisocyanate, diphenylsulphone-4,4'-diisocyanate,dichlorohexamethylene diisocyanate, furfurylidene diisocyanate,l-chlorobenzene- 2,4-diisocyanate and the like. Other suitablepolyisocyanates are among those mentioned, for example, in US. Pat. No,3,382,215. It is preferred that aromatic diisocyanates be used and forbest results, 4,4'-diphenylmethane diisocyanate or isomeric mixtures oftolylene diisocyanates have proven to be especially suitable.

As set forth hereinabove the chain extender of this invention isbis-(fl-hydroxyethoxyphenyl)methane, preferably, the para, para'-isomer.The chain extender of this invention is a known compound and may beprepared for example, by reacting phenol with ethylene oxide to formphenoxyethanol and reacting phenoxyethanol with formaldehyde in thepresence of hydrochloric acid to form the desiredbis-(,B-hydroxyethoxyphenyl)methane according to the followingequations:

HOCHzCHz-O-QCHzQ-O-CIEIzCHzOH As an example, the chain extender of thisinvention may be prepared in the following manner. About four molsphenoxyethanol, prepared by reacting phenol and ethylene oxide in aknown manner, about 1 mol of a 37% solution of formaldehyde and aboutm1. of concentrated hydrochloric acid are mixed and stirred at about 25C. to 30 C. for about 12 hours and subsequently heated at reflux forabout 6 hours. The mixture is then cooled to about room temperature andneutralized with a 30% NaOH solution. Excess phenoxyethanol is strippedoff at about C. C./15 mm. The main fraction is obtained by distillationat about 230 C.250 C./ 0.5 mm. and the product is recrystallized frombenzene. About a 65% to 70% yield of bis-(,B-hydroxyethoxyphenyl)methane having a melting point of about 104.5 C. is obtained.

In some cases it may be necessary to increase the rate of reaction ofthe active hydrogen containing organic compounds and the organicpolyisocyanate and if this is desired, one may use any suitable catalystfor the isocyanateactive hydrogen reaction, such as, for example,tertiary amines, such as N-ethylmorpholine, dimethyl benzyl amine,dimethyl stearyl amine, N,N-endoethylene piperazine, triethylene diamineand the like as Well as metal catalysts such as dibutyl tin dilaurate,dibutyl tin-di-2- ethyl hexoate, stannous octoate, stannous oleate, leadnaphthanate and the like and mixtures thereof.

The purpose of this invention is applicable to the prep aration ofelastomeric products by the various methods known to those skilled inthe art. Thus, the organic compound containing active hydrogen atoms,the polyisocyanate and the chain-extending composition can be mixedtogether in the proper proportions and cast in the usual castingtechnique into a mold having the desired configuration. Also, this sameresult can be accomplished by first reacting the polyisocyanate and theorganic compound containing active hydrogen atoms to obtain an -NCOterminated prepolymer and then mixing this prepolymer with thechain-extending composition in the casting technique.

In any case the reaction mixture is cast into a mold and it is cured atany suitable temperature and preferably at a temperature within therange of about 100 C. to about C., the curing time being somewhatdependent on the temperature at which curing is effected. Mostpreferably, the final mixture of reaction components is cast into a moldand cured at a temperature of about 110 C. for about 24 hours.

The process is also useful in the millable gum technique wherein theorganic compound containing active hydrogen atoms, the chain-extendingcomposition and a deficiency of the polyisocyanate are first reacted toform a millable used in the rubber industry, and the final productformed by a compression molding technique or the like. In this millablegum technique, a suitable peroxide such as, for example, dicumylperoxide may be incorporated into the millable gum to bring about thecross-linking.

In addition, the process of this invention is useful in what has beentermed the thermoplastic technique wherein the reaction compounds aremixed and caused to partially react. The reaction is then interruptedwhile the material can still be worked by thermoplastic techniques. Atthis point the material is generally in the solid state. This solidpartially reacted material can be fabricated into the desired final formby molding techniques such as, for example, compression molding,injection molding, extrusion, and the like. In this technique, as wellas in the casting and millable gum procedures, a one-shot mixing systemor a prepolymer procedure can be followed.

The individual reaction components and the proportion in which they areadded can be chosen according to the basic properties desired of the endproduct. However, it is preferred that the isocyanate be present in anamount sufiicient to react with all of the active hydrogen atoms presentand particularly in an amount such that a slight excess is present basedon the active hydrogen atoms present in the other reaction components.For best results, it is preferred that the isocyanate be present in anamount such that the NCO to active hydrogen ratio is from about 1.0 toabout 1.1.

UTILITY The polyurethane plastics obtained by the process of the presentinvention are useful in a variety of applications, such as, for example,the preparation of molded articles, tires, toys, shoe heels, bearings,gear wheels, valve seals, as insulated cable covering for electricalwire and the like.

EXAMPLES The invention is further illustrated but is not intended to belimited by the following examples in which all parts and percentages areby weight unless otherwise specified.

EXAMPLES 1-4 Elastomers were prepared by mixing polyester chainextenderand isocyanate in a molar ratio of about l:2:3.15 or 1:3.38:4.6respectively. The molar portion of a polyester having a molecular weightof about 2,000 and an OH number of about 58 prepared by condensing about1 mol of adipic acid with about 1.09 mols of glycol is dehydrated byheating to a temperature of about 125 C. and reacted with the molarportion of 4,4-diphenylmethane diisocyanate and the molar portion of thechain extender. The reaction mixture is pressed into a hot mold, removedand cured by heating to a temperature of about 110 C. for about 24hours. The resulting substantially homogeneous polyurethtne plasticsobtained exhibit the following physical characteristics as set forth inthe table below.

COMPARISON EXAMPLE For comparison purposes an elastomer is prepared in amanner similar to Example 4 except that p-phenylenedi(fi-hydroxyethylether) HOCHzCHr-O-QO-CIIzOHzOH is employed as the chainextender instead of bis(p-hydroxyethoxyphenyl)methane. When thiselastomer is hydrolyzed at 100 C. and 100% relative humidity theelastomer retains only 34% of its original tensile strength after 4 dayshydrolysis aging and completely falls apart after 7 days exposurewhereas the elastomer of Example 4 retains 95% of its original tensilestrength after 4 days exposure and after 7 days hydrolysis aging at 100%relative humidity and 100 C.

It is to be understood that any of the components and conditionsmentioned as suitable herein can be substituted for its counterpart inthe foregoing examples and that although the invention has beendescribed in considerable detail in the foregoing, such detail is solelyfor the purpose of illustration. Variations can be made in the inventionby those skilled in the art without departing from the spirit and scopeof the invention.

What is claimed is:

1. An elastomeric non-porous polyurethane polymer prepared by a processcomprising reacting a polyester containing hydroxyl groups reactive withNCO groups, said polyester having a molecular weight of from about 600to about 3000 and a hydroxyl number from about to about 35, and anexcess of an organic diisocyanate with a chain extender wherein saidchain extender is bis(B-hydroxyethoxyphenyl) methane in an amount suchthat the NCO to active hydrogen ratio is from about 1.0 to about 1.1.

2. The polymer of claim 1 wherein the organic diisocyanate is anaromatic diisocyanate.

3. The polymer of claim 2 wherein the aromatic diisocyanate is4,4-diphenylmethane diisocyanate.

4. The polymer of claim 1 wherein the organic diisocyanate is reactedwith the polyester containing active hydrogen atoms reactive with -NCOgroups in a first step to prepare an NCO terminated prepolymer andreacting said NCO terminated prepolymer withbis-(fi-hydroxyethoxyphenyl) methane.

5. The polymer of claim 1 wherein the chain extender is 4,4-bis-(fl-hydroxyethoxyphenyl)methane.

References Cited UNITED STATES PATENTS 3,577,385 5/1971 Feltzin et a1.260-47 3,012,992 12/1961 Pigott et al 260-75 3,164,565 1/ 1965 Calamari26047 3,357,954 12/1967 Kirkaldy 26075 3,436,361 4/1969 Wooster 260l8WILLIAM H. SHORT, Primary Examiner L. L. LEE, Assistant Examiner US. Cl.X.R.

26075 NP, 77.5 AM, 77.5 SP

